1. Field of the Invention
The present invention relates generally to an apparatus for treating a wafer. More particularly, this invention relates to an apparatus that can clean a wafer by applying a cleaning solution with ultrasonic oscillation and that can dry the wafer using a drying gas.
2. Description of the Related Art
Generally, a semiconductor device is manufactured by repeatedly performing a series of processes on a semiconductor wafer. These processes can include, for instance, a film deposition process, a photolithography process, an etching process, an ion implanting process, a polishing process, a cleaning process, and a drying process. The cleaning and the drying processes are typically performed to remove impurities or undesired films attached to the wafer and to dry the wafer during the other manufacturing processes. The cleaning and drying processes are becoming more important as the patterns formed on the wafer are becoming smaller and as the aspect ratio of the patterns are increasing.
Conventional wafer cleaning equipment includes batch cleaning apparatuses and single wafer rapid cleaning apparatuses. Batch cleaning apparatuses simultaneously clean a plurality of wafers while single wafer rapid cleaning apparatuses sequentially clean a plurality of wafers one wafer at a time.
Batch cleaning apparatuses have a cleaning bath that includes a cleaning solution used to simultaneously clean the plurality of wafers. An ultrasonic oscillation may be applied to the cleaning solution of the batch cleaning apparatus to increase the efficiency of the cleaning process. Single wafer rapid cleaning apparatuses have a chuck for supporting a wafer and nozzles for providing a cleaning solution to upper and lower faces of the wafer. In the single wafer cleaning apparatus, the cleaning solution is applied to the wafer. Ultrasonic oscillation may be applied to the cleaning solution on the wafer.
Although the single wafer rapid cleaning apparatus is more effective at cleaning the wafer than the batch cleaning apparatus, the cleaning time of the single wafer rapid cleaning apparatus is longer than that of the batch cleaning apparatus. Unfortunately, when a plurality of wafers is simultaneously cleaned using the batch cleaning apparatus, impurities removed from the plurality of wafers may not be drained from the cleaning bath. The impurities remaining in the cleaning bath may attach to the wafer, thereby reducing the effectiveness of the cleaning process. In addition, the batch cleaning apparatus may not remove the impurities between the minute patterns formed on the wafer.
One single wafer rapid cleaning apparatus that cleans wafers by applying megasonic energy to a cleaning fluid provided on the wafers is disclosed in U.S. Pat. No. 6,039,059 (“Bran”). The cleaning apparatus in Bran includes an elongated quartz probe for applying megasonic energy to the cleaning fluid. U.S. Laid Open Patent Publication No. 2001-32657 also discloses a megasonic treating apparatus having a megasonic transformer for applying mechanical oscillation to a cleaning solution or an etching solution provided on a wafer.
FIG. 1 is a cross-sectional view of a conventional single wafer rapid cleaning apparatus 100 having a quartz probe 160. Referring to FIG. 1, a wafer W is disposed on a round chuck 110, and a motor 120 rotates the chuck 110. The chuck 110 includes a circular ring 112 for supporting the wafer W, a hub 114 disposed on the upper face of a rotation shaft 122, and a plurality of spokes 116 connecting the circular ring 112 to the hub 114.
A first nozzle 130 is provided over the wafer W. The first nozzle 130 applies a cleaning solution to the wafer W. A bowl 140 encloses the chuck 110 to contain the cleaning solution that is scattered from the wafer W toward a peripheral region due to the rotation of the wafer W. A draining pipe 150 is connected to the bottom of the bowl 140 to drain the cleaning solution. A rotating shaft 122 extends through a central portion of the bottom of the bowl 140 to transfer the rotation force of the motor 120 to the chuck 110.
A quartz probe 160 having an elongated rod shape is disposed over the wafer W through a slot 140a formed in the bowl 140. The quartz probe 160 applies an ultrasonic oscillation to the cleaning solution provided on the wafer W. The quartz probe 160 extends parallel to the wafer W from the peripheral portion of the wafer W to the central portion of the wafer W, and is separated from the wafer W by a predetermined distance. In addition, a second nozzle 132 is installed through another portion of the bowl 140 to provide the bottom face of the wafer W on the chuck 110 with the cleaning solution.
In a cleaning process, after a wafer W is loaded onto the chuck 110, the motor 120 rotates the chuck 110 and the wafer W loaded thereon. A cleaning solution is provided onto the wafer W through the first and the second nozzles 130, 132. Rotation of the wafer W causes the cleaning solution provided onto the wafer W to be dispersed between the quartz probe 160 and the upper face of the wafer W. The quartz probe 160 applies ultrasonic oscillation to the cleaning solution located between the quartz probe 160 and the wafer W. Ultrasonic oscillation of the cleaning solution removes the minute particles attached to the wafer W. Chemicals can then be provided to the wafer W to remove any undesired film or impurities on the wafer W. Ultrasonic oscillation accelerates the chemical reaction with the undesired film or the impurities on the wafer W to increase the speed and effectiveness of their removal. Rotation of the wafer W also causes the cleaning solution to flow from the upper and lower faces of the wafer W. The cleaning solution is thereby transferred to the bottom of the bowl 140. The cleaning solution is then drained through the draining pipe 150 connected to the bottom portion of the bowl 140.
Unfortunately, the elongated rod-shaped quartz probes 160 of the apparatus 100 are frequently broken due to the ultrasonic oscillation. These quartz probes 160 therefore should not be lengthened beyond a certain length, and as a result, cannot be used effectively for large wafers. In addition, the amount of ultrasonic oscillation provided by the quartz probe 160 varies depending on the flow rate of the cleaning solution and the rotation speed of the wafer W. The ultrasonic oscillation may therefore not be uniformly applied to the cleaning solution provided on the wafer. The effectiveness of the cleaning process may therefore be different on different portions of the wafer W.
Furthermore, because the contacting area between the quartz probe 160 and the cleaning solution provided on the wafer W is limited, the effect of the ultrasonic oscillation may be reduced. Also, the minute patterns formed on the wafer W may be damaged due to the ultrasonic oscillation applied directly to the cleaning solution on the wafer W.